Abstract
This paper shows a two-element multiple-input–multiple-output (MIMO) circularly polarized antenna. The proposed design achieves polarization diversity by using two conventional truncated corner square patches. Since the operating bandwidth of the conventional design is extremely narrow, a metasurface is utilized for bandwidth enhancement. In the open literature, several MS-based MIMO antennas have been reported. However, these designs can achieve high isolation with wide spacing between the MIMO elements. For the proposed design, the configuration of the MS is modified so that high isolation can be obtained with smaller element spacing. The design concept is verified by measurements on a fabricated prototype. The measured operating bandwidth (BW), which is an overlap between −10 dB impedance and 3-dB axial ration BWs, is from 5.0 to 5.6 GHz (11.3%). Across this band, the isolation is always higher than 20 dB and the realized gain is higher than 4.4 dBi.